1. Field of the Invention
The present invention relates to laser devices, and in particular, to a lens, and a design method for a lens, that is capable of forming a laser beam having uniform energy distribution so that the laser beam can be distributed into laser lines of uniform brightness along a plane.
2. Description of the Prior Art
The structure of a conventional laser lens typically includes a light converting device at the emitting side of the laser beam of a laser beam emitter (or emitting module). The common light converting devices include convex lens, cylindrical lens, and multi-angle prisms, among others, which are utilized together with rotary elements or elements of other contours to extend a laser beam of point form into a laser line, a laser ring, or a laser light of different kinds. Such laser lights are primarily used for horizontal measurement, for distance measurement, or for indication, in the field of architectural engineering.
FIG. 1 illustrates a known laser point and line projecting device that is illustrated in Republic of China (Taiwan) Patent No. 491349. The laser point and line projecting device 10 provides two methods for converting laser beam into a laser line. A first method is to upright a light source vertically by arranging a point light-source projector 11 under a rotary motor 12, on top of which a pentagonal prism 13 is arranged. When the rotary motor 12 rotates, the pentagonal prism 13 converts the laser beam projected from the point light-source projector 11 into a laser ring 15. A second method is to arrange the light emitting side of another point light-source projector 14 at a rectangular hollow trough 141 to convert the laser beam into a laser line 16. However, the formation of the laser ring 15 must depend upon the rotation of the motor 12 driven by the power supply, so the size of the machine must be very large. Furthermore, the range of the laser line 16 is restrained by the rectangular hollow trough 141. After the laser line 16 is diffused, its brightness is concentrated in a central section, with the rest of the laser line 16 being fuzzy due to the elongation caused by the long distance from the center of the laser line 16, such that the brightness of the laser line 16 will not be uniform (i.e., the laser line 16 is brighter at the center), thereby negatively impacting the measurement.
FIG. 2 illustrates another example of a “Laser Line Generating Device” from WO 02/093108 A1. The laser line generating device 20 has a lens 22 that has a straight plane 222 and a convex plane 221. The lens 22 is arranged in front of the laser point light-source projector 21. When the laser beam 23 enters the lens 22, part of the laser light is refracted by the convex plane 221 to change its advancing direction to become a laser light 231 that is inclined downwardly. The laser light passing through the straight plane 222 is emitted in parallel to become a parallel laser light 232. The main purpose of WO 02/093108 A1 is to generate a fan-shaped laser light, the strength of which is similar to a “comet” shape, such that the emitted laser demarcating light will not be blocked by objects to affect measurement. In practice, since the curvature of the convex plane 221 can differ, the refracting angle of the laser light 231 can also differ. In this regard, if the curvature of the convex plane 221 is not correct, then the uniformity of the formed laser line will be adversely affected.